I know this has probably been posted abotu a half million times here, but the search function is still down, and I have a few questions...sorry.

I'm wanting to get some type of optic for my new Cav Arms 16" flat top. I'll probably use the DPMS rear sight. I'd like it to "co-witness" as you guys say. For the optic, I'm looking at the Aimpoint M2 line and the EOTech 512 and 552. Both are near the same price.

It looks like the EOTech will mount directly the the flat top as-is...will is co-witness like that? I've read from you guys that the 2D reticle isn't as fast as the dot...comments?

Looks like I'd have to buy a mount for the Aimpoint, and you guys really like the cantilever mount, but I can't get over the price of it. $170-200 for a mount??!!!!

Battery life is a concern, and that's why I'm looking at the EOTechs with AA batteries only.

So, which would you guys choose for a "fighting" optic? Is the Aimpoint worth the $170-$200 extra (mount)? Doesn't look like it from this angle.

I have an Eotech 552 mounted directly to my Colt M4 flattop with an ARMS #40 Buis and it co-witnesses perfectly. The only difference between the 552 and the 512 is the night vision compatability of the 552.

Get an ARMS 26M68 and spacer for about $100 and just use it without the spacer later when you upgrade later to a RAS 2 or a SIR.

That way if your optic gets mud on it you can rip that bad boy off post haste and stay in the fight.

Use a battery doubler on the M2 and you will have battery life like no other optic out there.

IMHO the cantilever mount does not make THAT big a difference. When you get the RAS 2 or SIR it is designed to be mounted in the cantilieverd spot and your rear sight and ring still work together. If you are considering an Eotech it sits MUCH frther back than the non cantilevered Aimpoint.

Dont quote me cause I dont have a 22M68 - but I think you need the full spacer - DevL?

It will work fine with either the ARMS#40 or the DPMS fixed - I recommend the #40 I have had some problmes with the lack of durability in the DPMS fixed - the screws are failry weak and can be easily damaged to the point the sight will get knocked off easily

The 1,000 hour battery life is rated if the site is on the highest power. The 10,000 hour rating is if the site is set to the lowest power. Realistically, you should expect somewhere right between those two extremes. Say 5,000 hours.